Perfume Studio Set (10 PCS) of True Amber Glass Roll Ons (Not Painted) With Glass Ball Applicators- 10 ml As opposed to plastic balls that are rigid and penetrable, risking contamination of your oils over time, glass balls are impenetrable and less susceptible to toxin contamination, and will give you the smoothest application on your skin. Additional Details ------------------------------ Product description: Perfume Studio Set of True Amber Glass Roll Ons (Not Painted) With Metal Ball Applicators- 10 ml As opposed to plastic balls that are rigid and penetrable, risking contamination of your oils over time, stainless steel metal and glass balls are impenetrable and less susceptible to toxin contamination, and will give you the smoothest application on your skin. Warranty description: 90-day guaranteed against leaks/defects. These perfume studio essential oil roll ons have been factory and field tested for leaks. If you encounter any leak problems or defects with these metal roller balls within 90 days of purchase, you may contact us for a free replacement/refund on your purchase.